It is known within the art that a load variation applied onto a surface or a body can be measured with the help of a transducer. A transducer converts a variation in one physical quantity, e.g. pressure, quantitatively into a variation in another physical quantity, e.g. voltage. The present invention relates to an improved transducer arrangement with transducers for converting load variations into voltage variations.
One particular embodiment of such transducers are so-called force-sensing resistors (FSRs). FSRs are well known within the art and can be used in numerous applications. Such force-sensing resistors usually include at least two electrodes with a force-sensitive material arranged there in-between. In case a load is applied onto an FSR the resistance of between the electrodes across the force-sensitive material varies. An electrical circuit coupled to the electrodes monitors the change in resistance.
According to a preferred application, FSRs can be arranged inside a shoe sole for measuring the force a person applies thereon, during walking, jumping and especially running. US 2010/0063778 reveals such a shoe sensor system with different force-sensing resistors, which are operatively connected to an electrical module. The electrical module is capable of gathering measurements from the different force-sensing resistors and of transmitting the data for further use via a communication port to an external device.
Yet, force-sensing resistors have a low speed response and can therefore only be used for measuring static loads or quasi-static load variations. They are not sufficiently precise to provide information about the user's foot anatomy or gait dynamics. This information however can be very useful in athlete monitoring or for healthcare applications, e.g. foot diagnosis and health prophylaxis.